1. Field of the Invention
The present invention relates to a backup power-source module, a backup power-source apparatus, and a computer, and more particularly to a backup power-source module for controlling a backup power source for supplying the power of a battery charged by AC input to an electronic device when the AC input is cut off, a backup power-source apparatus provided with the backup power-source module, and a computer using the power supplied from a battery.
2. Background Art
A personal computer (PC) has been frequently provided with a chip (hereinafter referred to as xe2x80x9ccore chipxe2x80x9d) on which a logic (hereinafter referred to as xe2x80x9cstate machinexe2x80x9d) for controlling power-source states of the PC, including internal register operations for storing the current power-source state of the PC is mounted, wherein the power-source states of the PC including on/off of the power source are controlled by the state machine of the core chip. An interface (I/F) with the state machine of the core chip is standardized. In a PC conforming to ACPI (Advanced Configuration and Power Interface), an I/F with a state machine is controlled by an operating system (OS). The power source of the PC is turned off by the OS which commands a power-source section through the state machine to turn off power after performing various types of power-off sequences.
Therefore, in the PC, a power source is not directly turned on or off by switching on/off a power switch in general but a power-on or power-off command is generated by the OS or by switching on/off the power switch to perform startup processing including power-on or termination processing including power-off.
However, a power source for supplying power to a PC may be cut off or may become unstable due to power-source troubles caused by various reasons which include, for example, artificial faults, influences of peripheral power-source conditions, and natural disasters. The artificial faults include mishandling of a power switch, accidental detachment of an AC plug, breaker action due to excessive current of a device, and leak breaker action. The influences of peripheral power-source conditions include drop of a power-source voltage and power-source noises. The natural disasters include power failure due to a thunderbolt.
When such a power-source trouble occurs, supply of power to a PC is unexpectedly cut off and a part of the software such as an OS or an application program might be corrupted if a power-source state is controlled by such software. If software, particularly an OS, or data and/or file managed by the OS is corrupted, it would be difficult to restart a PC and it may take a lot of time to restore the PC. Therefore, to back up power supply during a power failure, the number of PCs connected with an uninterruptible power system (UPS) is increasing.
The UPS has the function for automatically shifting a PC to a power cutoff state when a power failure occurs.
When a UPS is used and a power-supply source is turned on/off due to detachment of an AC plug or on/off action of a power switch, a battery built in the UPS is used and thus, the battery starts discharging. Therefore, when the battery built in the UPS is used, frequency of switching between charging and discharging of the battery is increased due to detachment of the AC plug or on/off action of the power switch, causing the lifetime of the battery to be shortened. Therefore, a technique has been proposed which stops discharging of a battery by detecting detachment of an AC plug from an AC outlet or detecting activation of a remote switch, as described in Published Unexamined Japanese Patent Application No. 8-251837.
However, a predetermined time interval is required between the switching off of the power switch and power-source cutoff when the PC performs power-cutoff processing after a power-off command is generated by the OS or by the switching off of the power switch and the termination processing is performed. The power-cutoff processing may not be smoothly performed by merely stopping discharging of the battery after the switching off of the power switch because, during this predetermine time interval, it is necessary to continuously supply power to the PC.
Moreover, when the battery in the UPS is used after the switching off of the power switch, frequency of switching between charging and discharging of the battery is increased so that the lifetime of the battery becomes shorter, as described above.
In view of the above, an object of the present invention is to provide a backup power-source module for backing up AC input without shortening the lifetime of a battery, a backup power-source apparatus provided with the module, and a computer using power supplied from the battery.
A feature of the present invention includes a backup power-source module that controls a backup power source for supplying power from a battery charged by an AC input to an electronic device when the AC input is cut off. The backup power-source module includes a selection which generates a selection signal for selecting power supplied by a battery when the electronic device is kept in an electrified state until the electronic device is shifted to a power cutoff state and there is no AC input. I.E., the selection signal causes the power supplied by the battery to be selected only when the electronic device is kept in a power cutoff state and there is no AC input.
Another feature of the present invention includes a backup power-source apparatus having a backup power-source module, a battery connected to the electronic device so that power can be supplied, a battery charger for charging the battery by the AC input, and a switch for switching power to be supplied to the electronic device between power from the AC input and power from the battery in accordance with the selection signal.
Still another feature of the present invention includes a computer having a function for backing up a power source by itself by incorporating the above described backup power-source apparatus into the computer.
Various other objects, features, and attendant advantages of the present invention will become more fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views.